Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation.

Odontoid fractures, especially unstable type II fractures have a poor prognosis in respect to healing. Therefore, operative stabilization (posterior fusion C1/2 or anterior screw fixation) has been suggested for the treatment of unstable type II and for some unstable type III fractures. Compared to posterior fusion C1/2, anterior screw fixation has proven to be effective; it has the advantage of leaving the motion segment C1/2 intact, therefore preserving at least some C1/2 rotation. However, in some instances, this method of stabilization is not indicated. In these cases, posterior fusion C1/2 is the treatment of choice. Primary posterior fusion C1/2 is indicated in (a) odontoid fracture associated with comminution of one or both atlanto-axial joints; (b) fracture of the odontoid associated with an unstable Jefferson fracture; (c) unstable type III odontoid fracture, when immobilization in a halo jacket or plaster cast is not suitable, as in elderly people or polytraumatized patients; (d) atypical type II fractures (comminuted or with oblique fracture in the frontal plane); (e) irreducible fracture dislocation C1/2, e.g., several-weeks-old fracture; (f) unstable type II or shallow and unstable type III odontoid fracture, when marked thoracic kyphosis is associated with limited extension of the cervical spine; (g) unstable type II or shallow type III odontoid fracture in elderly people with degenerative narrow spinal canal; (h) pathologic fracture of the odontoid. In all these instances, posterior fusion C1/2 is the treatment of choice. We prefer the transarticular screw fixation technique. Compared to other posterior fusion techniques, it has the advantage of increased stability and allows effective stabilization of C1/2 in a reduced position as well as immediate ambulation with minimal head support. This technique can also be performed when the posterior arch of the atlas is fractured or absent. Our experience of 12 acute odontoid fractures, managed by this technique, is presented. At follow-up, all C1/2 fusions were united in reduced position.